Client Downloader Tool for IIS 7

If the disk is slowing things down there are things you can do, but at some point you have to serve the content. You could do mirror sites or even better a cdn.

There are download accelerators / managers available as plug-ins for your clients browsers. They use basic compression but allow for restartable downloads and use multiple connections to max the bandwidth on the client end.
Simple Google search would show you what's available. Another expert may have a suggestion.

If you have something of economic value and a budget for this, consider Akamai.  But keep in mind that the speed of any download is only as fast as its slowest link.  If you have clients on slow internet connections, nothing you can do will improve their experience.

I see on some sites that there is a system to select all of the files that you want to download and the files are added to some sort of download manager.  Then, the client installs the "thin" download manager and starts the download.  The throughput is much faster through the download manager compared to downloading the files directly from the site.  Why is it so much faster?  I was curious if the download manager optimizes the transfer by possibly using multiple threads?  (example: support.dell.com)  

I understand that if I were to implement a solution like a download manager, this would introduce an additional software layer on the server side in addition to a back-end database of all of the downloadable files.  Remember, right now I'm just directing users to files via IIS directory browsing.  

There has to be a more elegant solution that would optimize the transfer rate.  Also, I do have the option to allocate a budget to a possible solution.

When you use a download manager as a plugin to the browser its main advantage is multiple threads or connections if the server allows it-.-some web servers will only allow a few connections from an IP at any one time. But this method requires you to do nothing on your server.
In Dell's case, I'm guessing they do have server side software to handle the download connections.
I would see how you go with a simple download manager on your clients.
As Ray has indicated, it's worth finding out where the bottle neck is in terms of bandwidth. If your finding its your internet connection that is slowing things down then it's probably time to move to a cloud based solution that will have a bigger "pipe"

Thanks.